The present invention relates to a device and a method for mobile radio communication, and in particular, to a mobile radio communication system, a mobile radio communication method and a base station controller employing data selection process.
Mobile stations such as portable cellular phones have become widely available these days, and mobile stations according to CDMA (Code Division Multiple Access) have been popular today because of their fine speech quality.
FIG. 1 shows an example of a CDMA mobile radio communication system. The mobile communication system shown in FIG. 1 includes a mobile station (MS) 101, radio base stations (BS""s) 102A, 102B, 102C and 102D, base station controllers (BSCs) 104 and 105, and a mobile services switch center (MSC) 108. The radio base stations 102A, 102B, 102C and 102D take charge of mobile service areas 103A, 103B, 103C and 103D, respectively. The radio base stations 102A and 102B are connected to the base station controller 104, and the radio base stations 102C and 102D are connected to the base station controller 105.
In the CDMA mobile radio communication system of FIG. 1, upstream data which is transmitted by the mobile station 101 which is located in the mobile service areas 103A and 103B is received by the radio base stations 102A and 102B, and the radio base stations 102A and 102B send the received data to the base station controller 104. The base station controller 104 which receives the upstream data of the mobile station 101 from the radio base stations 102A and 102B executes xe2x80x9cselection process for diversity hand-overxe2x80x9d with regard to the received upstream data, according to timing which is provided in sync with radio frames. In the selection process, the base station controller 104 selects the upstream data from the radio base station 102A or the upstream data from the radio base station 102B based on radio quality information which is supplied from the radio base stations 102A and 102B. After the selection process is finished, the base station controller 104 sends the selected upstream data to the mobile services switch center 108.
However, if there is a difference of data transmission time between the line from the radio base station 102A to the base station controller 104 and the line from the radio base station 102B to the base station controller 104 (for example, if the data transmission from the radio base stations 102A and 102B to the base station controller 104 is executed by means of ATM (Asynchronous Transfer Mode) data transmission and variations in cell delay occur), the base station controller 104 has to execute the selection process after waiting for the slowest upstream data corresponding to the longest data transmission time. While the base station controller 104 waits for the slowest upstream data, faster upstream data have to be temporarily stored in a buffer of the base station controller 104, thereby processing delay due to the data buffering occurs.
Further, when the mobile station 101, which has been located in the mobile service areas 103A and 103B and executing communication with the radio base stations 102A and 102B under the base station controller 104 (anchor-side base station controller (that is, a base station controller which started the communication with the mobile station 101 first)), moves into other mobile service areas 103C and 103D and starts communication with other radio base stations 102C and 102D under another base station controller 105 (drift-side base station controller) as shown in FIG. 1, a large number of connections become necessary if connections are established from the anchor-side base station controller 104 to all the radio base stations 102C and 102D which are communicating with the mobile station 101 under the drift-side base station controller 105. Therefore, in such cases, the selection process is executed first in the drift-side base station controller 105 and only the selected upstream data is sent to the anchor-side base station controller 104, and thereafter the selection process is executed again in the anchor-side base station controller 104.
However, in the above method employing two stages of selection processes at the drift-side base station controller 105 and the anchor-side base station controller 104, much data buffering time occurs in the drift-side base station controller 105 and the anchor-side base station controller 104, and thereby delay is caused in the mobile radio communication service.
It is therefore the primary object of the present invention to provide a mobile radio communication system, a mobile radio communication method and a base station controller employing the selection process for diversity hand-over, by which the wait delay for the selection process in the case of the inter-BSC (Base Station Controller) handover can be decreased and thereby the processing delay can be minimized.
In accordance with a first aspect of the present invention, there is provided a mobile radio communication system comprising: mobile stations; radio base stations which communicate with the mobile stations via connections on radio waves; base station controllers for controlling radio base stations thereunder, each of which including an upstream selection process section for executing a selection process, in which received upstream data which have been transmitted by a mobile station and supplied from radio base stations thereunder to the base station controller are temporarily stored in a buffer and data having the highest quality is selected from the stored upstream data corresponding to the same radio frame based on radio quality information and the selected data having the highest quality is sent to the next upper device; and mobile services switch centers each of which is provided as the interface between a network and base station controllers which are connected thereunder. In the mobile radio communication system, the operation mode of the upstream selection process section of the base station controller can be set to through mode with respect to a mobile station. When the operation mode of an upstream selection process section of a base station controller is the through mode with respect to a mobile station and the upstream selection process section received upstream data transmitted by the mobile station from a radio base station thereunder or a lower base station controller which is communicating with the base station controller, the upstream selection process section directly sends the received upstream data to the next upper device without temporarily storing the received upstream data and executing the selection process.
In accordance with a second aspect of the present invention, in the first aspect, the operation mode of the upstream selection process section of the base station controller is set to normal mode with respect to a mobile station and thereby the selection process is executed normally with respect to the mobile station when a communicating connection number with respect to the mobile station, which means the number of radio base stations and lower base station controllers which are communicating with the base station controller with respect to the mobile station, is 2 or more. The operation mode of the upstream selection process section is set to the through mode with respect a mobile station when the communicating connection number with respect to the mobile station is 1.
In accordance with a third aspect of the present invention, in the first aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller, the operation mode of the upstream selection process section of the second base station controller is set to the through mode with respect to the mobile station.
In accordance with a fourth aspect of the present invention, in the first aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller and thereby the first base station controller finishes the communication with the radio base station thereunder and thereafter executes communication with the another radio base station under the second base station controller, the operation mode of the upstream selection process section of the first base station controller is set to the through mode with respect to the mobile station.
In accordance with a fifth aspect of the present invention, in the first aspect, the communication between the mobile station and the radio base stations is executed by means of CDMA (Code Division Multiple Access).
In accordance with a sixth aspect of the present invention, there is provided a base station controller for controlling radio base stations thereunder which communicate with mobile stations via connections on radio waves. The base station controller includes an upstream selection process section which includes an upstream data reception means, a timing control means, a selection process means, an upstream frame transmission means and a control means. The upstream data reception means receives upstream data which have been transmitted by a mobile station, received by one or more radio base stations and supplied from the radio base stations or another lower base station controller to the base station controller. The timing control means provides processing timing for selection process to the selection process means. The selection process means is provided with functions for operating depending on whether the present operation mode with respect to a mobile station is normal mode or through mode when the upstream data reception means received upstream data transmitted by the mobile station, storing/reading upstream data to/from a received data buffer and executing the selection process for upstream data according to the processing timing which is provided by the timing control means. The upstream frame transmission means transmits the upstream data outputted by the selection process means to the next upper device. The control means controls the operations of the upstream frame reception means, the upstream frame transmission means, the selection process means and the received data buffer. When a communicating connection number with respect to a mobile station, which means the number of radio base stations and lower base station controllers which are communicating with the base station controller with respect to the mobile station, is 2 or more, the operation mode of the upstream selection process section of the base station controller is set to normal mode with respect to the mobile station and thereby the selection process is executed by the selection process means normally with respect to the mobile station. When the communicating connection number with respect to a mobile station is 1, the operation mode of the upstream selection process section is set to the through mode with respect the mobile station and thereby the received upstream data is directly transmitted to the next upper device without temporarily storing the received upstream data in the received data buffer and executing the selection process.
In accordance with a seventh aspect of the present invention, there is provided a mobile radio communication method for a mobile radio communication system which is provided with: mobile stations; radio base stations which communicate with the mobile stations via connections on radio waves; base station controllers for controlling radio base stations thereunder, each of which including an upstream selection process section for executing a selection process, in which received upstream data which have been transmitted by a mobile station and supplied from radio base stations thereunder to the base station controller are temporarily stored in a buffer and data having the highest quality is selected from the stored upstream data corresponding to the same radio frame based on radio quality information and the selected data having the highest quality is sent to the next upper device; and mobile services switch centers each of which is provided as the interface between a network and base station controllers which are connected thereunder. In the mobile radio communication method, the operation mode of the upstream selection process section of the base station controller is set to through mode with respect to a mobile station when necessary. When the operation mode of an upstream selection process section of a base station controller is the through mode with respect to a mobile station and the upstream selection process section received upstream data transmitted by the mobile station from a radio base station thereunder or a lower base station controller which is communicating with the base station controller, the upstream data received by the upstream selection process section is directly sent to the next upper device without temporarily storing the received upstream data and executing the selection process.
In accordance with an eighth aspect of the present invention, in the seventh aspect, the operation mode of the upstream selection process section of the base station controller is set to normal mode with respect to a mobile station and thereby the selection process is executed normally with respect to the mobile station when a communicating connection number with respect to the mobile station, which means the number of radio base stations and lower base station controllers which are communicating with the base station controller with respect to the mobile station, is 2 or more. The operation mode of the upstream selection process section is set to the through mode with respect a mobile station when the communicating connection number with respect to the mobile station is 1.
In accordance with a ninth aspect of the present invention, in the seventh aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller, the operation mode of the upstream selection process section of the second base station controller is set to the through mode with respect to the mobile station.
In accordance with a tenth aspect of the present invention, in the seventh aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller and thereby the first base station controller finishes the communication with the radio base station thereunder and thereafter executes communication with the another radio base station under the second base station controller, the operation mode of the upstream selection process section of the first base station controller is set to the through mode with respect to the mobile station.
In accordance with an eleventh aspect of the present invention, in the seventh aspect, the communication between the mobile station and the radio base stations is executed by means of CDMA (Code Division Multiple Access).